SZ observations with AMI of the hottest galaxy clusters detected in the XMM-Newton Cluster Survey

TL;DR

This study uses AMI to observe the Sunyaev-Zel'dovich effect in the hottest galaxy clusters from the XMM-Newton survey, finding significant detections in a few and setting upper limits for others, revealing lower large-scale temperatures than X-ray estimates.

Contribution

First application of deep SZ observations with AMI to the hottest XCS clusters, providing new insights into their large-scale properties and temperature discrepancies.

Findings

SZ effect detected in 3 clusters at high significance

Large-scale temperatures are lower than X-ray core temperatures

Upper limits on temperature for undetected clusters

Abstract

We have obtained deep SZ observations towards 15 of the apparently hottest XMM Cluster Survey (XCS) clusters that can be observed with the Arcminute Microkelvin Imager (AMI). We use a Bayesian analysis to quantify the significance of our SZ detections. We detect the SZ effect at high significance towards three of the clusters and at lower significance for a further two clusters. Towards the remaining ten clusters, no clear SZ signal was measured. We derive cluster parameters using the XCS mass estimates as a prior in our Bayesian analysis. For all AMI-detected clusters, we calculate large-scale mass and temperature estimates while for all undetected clusters we determine upper limits on these parameters. We find that the large- scale mean temperatures derived from our AMI SZ measurements (and the upper limits from null detections) are substantially lower than the XCS-based core-temperature estimates. For clusters detected in the SZ, the mean temperature is, on average, a factor of 1.4 lower than temperatures from the XCS. For clusters undetected in SZ, the average 68% upper limit on the mean temperature is a factor of 1.9 below the XCS temperature.